1. Field of the Invention
This invention relates to medical scanning apparatus and more particularly to a novel and improved ultrasonic scanning system useful for visualizing the condition of internal organs of a patient or the like.
2. Description of the Prior Art
Ultrasonic scanning of a test object in order to examine its interior structure is known in the art. Such ultrasonic scanning relies on the use of a transducer which transmits ultrasonic energy into a subject and receives reflections of that transmitted energy. These reflections are then converted to electrical signals which typically are transmitted to a display apparatus where an image is produced on a cathode ray tube screen.
In medical diagnosis it is now routine to position a transducer in contact with a patient for conducting a study. The transducer is then rocked about an axis passing along the face of the transducer to scan a sector. The most widely used apparatus and technique used for this purpose is disclosed and claimed in U.S. Pat. No. 3,924,452 issued to Meyer and Wright on Dec. 9, 1975 and entitled "Sector Scanning Ultrasonic Inspection Apparatus".
Cardiac studies are difficult with prior apparatus such as that disclosed in the referenced patent and other devices for two major reasons. These reasons are:
1. The transducer should be pivoted quite rapidly to produce useful images. This requirement is due in large part to the rapid movement of the heart; and, PA1 2. The transducer must be small and capable of accurate positioning at one of a few locations each between ribs of the patient.
Sector scanning devices have been proposed which are intended to be used primarily, if not exclusively, for cardiac studies. With these devices the rocking action of the transducer is achieved mechanically rather than manually as in the referenced patent. In some of these units the magnitude of sector scan is adjustable. When the sector scanning angle is relatively large a relatively broad area of the patient may be surveyed. When something of interest is noted the sector scanning angle may be reduced to focus on the region of interest. Prior units have required that the scanning operation be temporarily stopped when it was desired to adjust the magnitude of the sector being surveyed.